Process for the manufacture of



Patented Dec. 31, 1940 PATENT OFFICE PROCESS FOR THE MANUFACTURE OF DRYING OILS Itemmet Priester, Deventer, Netherlands, assignor to Naamlooze Vcnnootschap Industrleele Maatschamr i Voorheen No Deventer, Netherlands No Drawing.

8 Claims.

The present invention relates to the manufacture of drying oils from oils having one or more hydroxy groups in the fatty acid radical, castor oil being the best known representative of this group of oils.

Prior to the present invention it was already known to convert those oils having one or more hydroxy groups in the fatty acid radical into drying oils by splitting oil water from the fatty acid radical.

It has been proposed to carry out the aforesaid process in two steps, by first liberating the fatty acid from the oil, converting this fatty acid by heating at a temperature of say 260 0. into an unsaturated acid with two double bonds in a conjugated neighbouring position and thereafter esterifying the acid thus obtained with a suitable alcohol.

However, it will be understood, that it is far more economical to convert the oils having a hydroxy group in the fatty acid radical into a drying oil in one step. This is done according to known processes by heating the oil to approximately 200 C. in the presence of some percents by weight of catalysts, such as bleaching clay (fullers earth), toluene sulpho-chloride, phosphoric acid, silicic acid, boric acid or an aromatic disulphonic acid.

I have now found that oils having a hydroxy group in the fatty acid radical may easily be converted into drying oils in a particularly advantageous manner by heating said oils substantially above C. after thoroughly mixing the same with a small quantity of about 0.1% to 1% by weight of a catalyst selected from the following group: persulphuric acid, permonosulphuric acid, their anhydrides and their salts.

It will be understood that the term persulphuric acid compound comprises all percompounds of sulphiu'ic acid and their derivatives, and also the anhydrides and salts of same, e. g. potassium, sodium and ammonium persulphate. Without being desirous of connecting the process according to the application with any theory it should be pointed out, that especially those substances, as described above, having oxidizing properties, are advantageously suitable as catalysts, the action of the active oxygen apparently enhancing the speed of the reaction.

The quantity of the catalyst employed, efi'ecting the splitting oil of water, depends chiefly on the nature of the catalyst. The per-compounds of sulphuric acid are used in a very small amount, namely from 0.1% to 1% by weight. I have found that the quantity of catalyst should be seury & Van Der Lande, Netherlands, a company of the Application December '23, 1937, Serial No. 181,467. In the Netherlands January lected with regard to the color desired in the final product, since when too much of the catalyst is used, drying oils of dark color are obtained. Furthermore a tendency towards undesired decomposition of the drying oil is observed, if too much catalyst is used.

The process according to the present invention may be carried out at temperatures as low as 150 C., at which temperature the reaction starts by splitting oil water from the fatty acid radical ried out at a somewhat higher temperature, e. g. at C. at which temperature the reaction takes place faster. In continuing the heating, the temperature is raised gradually to about 230 to 240 C.; the temperature may, however, be increased up to 250 to 260 0., without side-reactions arising such as decomposition of the oil. It is a well-known fact that, for example, castor oil, heated alone, does not start to decompose until at 270- -280 C. under formation of oenanthol and undecylenic acid. However, if the splitting oil of water is effected with the aid of the catalysts herein described, the temperature may be increased up to 270 C., or even to 300 C. without danger of undesired decomposition-reactions. By heating the drying oils obtained in my process at a temperature of say 280-300 C., a heat polymerisation process takes place, similar to the heat polymerisation of linseed oil (stand oil formation).

The working conditions, such as the reaction temperature and the duration of the heating, are dependent on the nature and the amount of catalyst employed and on the desired properties of the oil to be prepared by the process. Normally the reaction (formation of a satisfactory drying oil) is finished in about 45 hours. If the process is followed by a further heating process in order to cook a stand oil, the first heating process may be shortened. It will also be clear from the foregoing, that the process according to the present invention may be carried out by diiierent modifications of working: It is frequently preferable to effect the heating process while stirring and applying a vacuum or while passing a current of an inert gas such as carbon dioxide or nitrogen, or steam, or another vapour through the reaction vessel, both these modifications providing a quick removal of the easily volatile constituents during the process. The vacuum applied will advantageously be as high as is possible on a technical scale.

The drying oil obtained by the present process has excellent drying properties, which are com- 10' of the oil. Preferably the heating process is car- Example 1 A Castor oil is heated under a vacuum of 10-20 mm. of mercury .while stirring with 0.4% by weight of potassium persulphate. Water starts to be given oil at about 190 C., the temperature is slowly increased to about 230-240 C., until the reaction is finished, that is until practically no more water is evolved. Foaming ceases and a thin fluid oil with a bright yellow colour is obtained, after removing the catalyst e. g. by filtration. The oil may be converted into a quickdrying product by means of the customary siccatives. If desired, the oil may be brought to stand oil-thickness by continuing the heating process under vacuum for 3 hours at 280 C. This oil possesses valuable properties for the varnish, linoleum and similar industries. All products thus obtained are distinguished by a good drying capacity, a high gloss, a good adhesive capacity and especially by a great resistance to water, weak alkalies and acids.

Example 2 The triglyceride of hydroxystearic acid obtained by hydrogenation of castor oil is thoroughly mixed with 0.3 percent by weight of finely divided potassium persulphate. After a homogeneous mixture is obtained, the same is heated to 180 C. after which the temperature is raised slowly to 250 C. which temperature is maintained for 4 hours. Gradually increasing quantities of water are distilled off until the reaction is finished. The catalyst may be removed by means of filtration, settling and decantation or centrifuging. A thin and limpid oil with good drying properties is obtained in good yield.

What I claim is:

1. The process of producing a drying oil from an oil having at least one hydroxyl group in the fatty acid radical, which comprises heating said all in the presence of a quantity not exceeding a few percent by weight of at least one persulphuric masses acid compound, until substantial drying properties are developed in said oil.

-2. The process of producing a drying oil from castor oil which comprises heating said castor oil with at least one persulphuric acid compound, and continuing the heating operation until the oil acquires useful drying properties.

3. The process of producing a drying oil from a glyceride oil having at least one hydroxyl group in the fatty acid radical which process comprises heating said oil in'the presence of only a small fraction of one percent of at least one persulphuric acid compound while passing a current oi. a chemically inert gas through the reaction mixture, and continuing said treatment until satisfactory drying properties are developed in said oil.

4. The process of producing a drying oil from an oil having one or more hydroxy groups in the fatty acid radical which comprises heating said oil at a temperature of 190 to 240 C., with at least one persulphuric acid compound, and continuing the said treatment until a drying oil is produced.

5. The process of producing a drying oil from 'an oil having at least one hydroxyl group in the fatty acid radical which comprises heating said oil under reduced pressure with at least one persulphuric acid compound, the heating being continued until a well drying oil remains.

6. The process of producing a drying oil from an oil having at least one hydroxyl group in the fatty acid radical, which comprises heating such an oil at a temperature of at least 230 C. with not more than a few per cent of at least one persulphuric acid compound. while passing a current of a chemically inert gas through the reaction mixture, and continuing the heating until a drying oil remains.

'7. The process of producing a drying oil from castor oil which comprises heating castor oil at a temperature of 180 to 240 C. with only a small fraction of one percent of a persulphate, and continuing the heating of the oil until an oil havin useful drying properties results.

8. The process of producing drying oils from oils having one or more hydroxy groups in the fatty acid radical which comprises heating said oils at a temperature of l80-240 C., under reduced pressure, with at least one persulphuric acid compound, while passing a current of a chemically inert gas through the reaction mixture, said treatment being continued until a drying oil is produced.

REMMET PRIESTER. 

